PTH has significant and diverse effects on bone metabolism. Intermittent low-dose PTH has anabolic effects on bone, whereas continuous high-dose PTH increases bone resorption and decreases bone formation. Because PTH acts primarily through only one receptor, intermittent and continuous PTH should initiate the same signaling pathways and thus induce the same primary genes. However, published data suggest that the temporal, pattern and magnitude of primary gene induction differs in cases of intermittent vs. sustained signaling. Through representational difference analysis, differences in gene expression between control and PTH-treated osteoblasts at the mRNA level have been examined in this laboratory. Fragments of two primary genes, PTH inducible fragment 1 and 1 (pif1 and Pif2) have been identified that do not match any known sequences in the NIH databank. The objective of this study is to identify the entire sequences of pif1 and pif2 and to study their regulation of PTH. These studies may elucidate the mechanisms of PTH's anabolic effects on bone.